MySQL socket loss?

Question

linux

Sometimes an error pops up

Mysql connect error [localhost, 127.0.0.1]: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) (400)

I tried to restart MySQL, but then I noticed that MySQL was running. lsof shows several lines with mysqld.
I tried to create a symbolic link in /tmp, but I get an error

ln: creating symbolic link `/var/lib/mysql/mysql.sock': File exists

I have rights and owners for folders mysql, socket. Nothing helped.
VPS 2 cores 2.6 GHz, 1 GB RAM, Centos 6.7, MySQL 5.5.45, Apache 2.4.16, Nginx 1.8.0, 1C-Bitrix
load average is very often higher than 2.5-3. Often above 5-6.
my.cnf. this is essentially my-medium.cnf with a few lines added

[client]
#password = your_password
port = 3306
socket = /var/lib/mysql/mysql.sock
# Here follows entries for some specific programs
# The MySQL server
[mysqld]
port = 3306
bind-address = localhost
socket = /var/ lib/mysql/mysql.sock
skip-external-locking
key_buffer_size = 16M
max_allowed_packet = 16M
table_open_cache = 100
sort_buffer_size = 512K
net_buffer_length = 8K
read_buffer_size = 256K
read_rnd_buffer_size = 512K
myisam_sort_buffer_size = 8M
wait_timeout = 600
join_cache
joinMache2
tmp_table_size = 32M
max_heap_table_size = 32M
thread_cache_size = 4
transaction-isolation = READ-COMMITTED
innodb_flush_method = O_DIRECT
log-bin=mysql-bin
binlog_format=mixed
server-id = 1
innodb_flush_log_at_trx_commit = 2
[mysqldump] quickauto
max_allowed_packet =
32M -rehash # Remove the next comment character if you are not familiar with SQL #safe-updates [myisamchk] key_buffer_size = 20M sort_buffer_size = 20M read_buffer = 2M write_buffer = 2M [mysqlhotcopy] interactive-timeout

httpd.conf

ServerTokens OS
ServerRoot "/etc/httpd"
PidFile run/httpd.pid
Timeout 30
KeepAlive Off
MaxKeepAliveRequests 2048
KeepAliveTimeout 5
StartServers 1
MinSpareServers 2
MaxSpareServers 8
MaxClients 25 #
ServerLimit 40
MaxRequestsPerChild 4096
# #
StartServers 2
# MaxClients 200
# 2Spare5 MinThreads ThreadsPerChild 25 # MaxRequestsPerChild 4000 # # # StartServers 8 # MinSpareServers 5
# MaxSpareServers 20
# ServerLimit 256
# MaxClients 256
# MaxRequestsPerChild 4000
#
#LoadModule auth_basic_module modules / mod_auth_basic.so
#LoadModule auth_digest_module modules / mod_auth_digest.so
#LoadModule authn_file_module modules / mod_authn_file.so
#LoadModule authn_alias_module modules / mod_authn_alias.so
#LoadModule authn_anon_module modules / mod_authn_anon.so
#LoadModule authn_dbm_module modules/mod_authn_dbm.so
#LoadModule authn_default_module modules/mod_authn_default.so
# do not disable
LoadModule authz_host_module modules/mod_authz_host.so
#LoadModule authz_user_module modules/mod_authz_user.so
Authz_owner_module the modules #LoadModule / mod_authz_owner.so
#LoadModule authz_groupfile_module the modules / mod_authz_groupfile.so
#LoadModule authz_dbm_module the modules / mod_authz_dbm.so
#LoadModule authz_default_module the modules / mod_authz_default.so
#LoadModule ldap_module the modules / mod_ldap.so
#LoadModule authnz_ldap_module the modules / mod_authnz_ldap.so
#LoadModule include_module modules/mod_include.so
# do not disable
LoadModule log_config_module modules/mod_log_config.so
#LoadModule logio_module modules/mod_logio.so
#LoadModule env_module modules/mod_env.so
#LoadModule ext_filter_module modules/mod_ext_filter.so
#LoadModule mime_magic_module modules/mod_mime_magic.so
# not turn off
LoadModule expires_module modules/mod_expires.so
LoadModule deflate_module modules/mod_deflate.so
LoadModule headers_module modules/mod_headers.so
#LoadModule usertrack_module modules/mod_usertrack.so
# don't disable
LoadModule setenvif_module modules/mod_setenvif.so
LoadModule mime_module modules/mod_mime.so
#LoadModule dav_module modules /mod_dav.so
# do not disable
LoadModule status_module modules/mod_status.so
LoadModule autoindex_module modules/mod_autoindex.so
#LoadModule info_module modules/mod_info.so
#LoadModule dav_fs_module modules/mod_dav_fs.so
#LoadModule vhost_alias_module modules/mod_vhost_alias.so
# do not disable
LoadModule negotiation_module modules/mod_negotiation.so
LoadModule dir_module modules/mod_dir.so
#LoadModule actions_module modules/mod_actions.so
#LoadModule speling_module modules/mod_speling.so
#LoadModule userdir_module modules/mod_userdir.so
# don't disable
LoadModule alias_module modules/mod_alias.so
LoadModule rewrite_module modules/mod_rewrite.so
LoadModule proxy_module modules/mod_proxy.so
#LoadModule proxy_balancer_module modules/mod_proxy_balancer.so
#LoadModule proxy_ftp_module modules/mod_proxy_ftp.so
#LoadModule proxy_http_module modules/mod_proxy_http.so
#LoadModule proxy_connect_module modules/mod_proxy_connect.so
#LoadModule cache_module modules/mod_cache.so
#LoadModule suexec_module modules/mod_suexec.so
#LoadModule disk_cache_module modules/mod_disk_cache.so
#LoadModule file_cache_module modules/mod_file_cache.so #LoadModule mem_cache_module modules/mod_mem_cache.so #LoadModule cgi_module modules/mod_cgi.so
#LoadModule cgi_module modules/mod_cgi.so
#LoadModule cgi_module modules/
mod_cgi.so version_module modules/mod_version.so
Include conf.d/*.conf
ExtendedStatus On
User apache
Group apache
ServerAdmin [email protected]
UseCanonicalName Off
DocumentRoot "/var/www/html"
Options SymLinksIfOwnerMatch
AllowOverride None
Options Indexes SymLinksIfOwnerMatch
AllowOverride None
Order allow,deny
Allow from all
UserDir public_html
DirectoryIndex index.php index.htm index.html
AccessFileName .htaccess
Order allow,deny
Deny from all
TypesConfig /etc/mime.types
DefaultType text/plain
MIMEMagicFile conf/magic
HostnameLookups Off
ErrorLog logs/error_log
LogLevel warn
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combin$
LogFormat "%h %l %u %t \"%r\" %>s %b" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent
LogFormat "%b"bytes
CustomLog logs/access_log combined
ServerSignature On
Alias ​​/icons/ "/var/www/icons/"
Options Indexes MultiViews
AllowOverride None
Order allow,deny
Allow from all
AllowOverride None
Order allow,deny
Allow from all
ScriptAlias ​​/cgi-bin/ "/var/www/cgi-bin/ "
AllowOverride None
Options ExecCGI
Order allow,deny
Allow from all
IndexOptions FancyIndexing VersionSort NameWidth=* HTMLTable
AddIconByEncoding (CMP,/icons/compressed.gif) x-compress x-gzip
AddIconByType (TXT,/icons/text.gif) text/*
AddIconByType (IMG,/icons/image2.gif) image/*
AddIconByType (SND,/icons/sound2.gif) audio/*
AddIconByType (VID,/icons/movie.gif) video/*
AddIcon /icons/binary.gif .bin .exe
AddIcon /icons/binhex.gif .hqx
AddIcon /icons/tar.gif .tar
AddIcon /icons/world2.gif .wrl .wrl.gz .vrml .vrm .iv
AddIcon /icons/compressed.gif .Z .z .tgz .gz .zip
AddIcon /icons/a.gif .ps .ai .eps
AddIcon /icons/layout.gif . html .shtml .htm .pdf
AddIcon /icons/text.gif .txt
AddIcon /icons/c.gif .c
AddIcon /icons/p.gif .pl .py
AddIcon /icons/f.gif .for
AddIcon /icons/dvi .gif .dvi
AddIcon /icons/uuencoded.gif .uu
AddIcon /icons/script.gif .conf .sh .shar .csh .ksh .tcl
AddIcon /icons/tex.gif .tex
AddIcon /icons/bomb.gif core
AddIcon /icons/back.gif ..
AddIcon /icons/hand.right.gif README
AddIcon /icons/folder.gif ^^DIRECTORY^^
AddIcon /icons/blank.gif ^^BLANKICON^^
DefaultIcon /icons/unknown.gif
ReadmeName README.html
HeaderName HEADER.html
IndexIgnore .??* *~ *# HEADER* README* RCS CVS *,v *,t
AddLanguage ca .ca
AddLanguage cs .cz .cs
AddLanguage da .dk
AddLanguage de .de
AddLanguage el . el
AddLanguage en .en
AddLanguage eo .eo
AddLanguage es .es
AddLanguage et .et
AddLanguage fr .fr
AddLanguage he .he
AddLanguage hr .hr
AddLanguage it .it
AddLanguage ja .ja
AddLanguage ko .ko
AddLanguage ltz .ltz
AddLanguage nl .nl
AddLanguage nn .nn
AddLanguage no .no
AddLanguage pl .po
AddLanguage pt .pt
AddLanguage pt-BR .pt-br
AddLanguage ru .ru
AddLanguage sv .sv
AddLanguage zh-CN .zh -cn
AddLanguage zh-TW .zh-tw
LanguagePriority en ca cs da de el eo es et fr he hr it ja ko ltz nl nn no pl p$
ForceLanguagePriority Prefer Fallback
AddDefaultCharset UTF-8
AddType application/x-compress .Z
AddType application /x-gzip .gz .tgz
AddType image/x-icon .ico
AddType text/html .shtml
AddOutputFilter INCLUDES .shtml
ErrorDocument 403 /error/403.html
ErrorDocument 404 /error/404.html
ErrorDocument 500 /error/50x.html
ErrorDocument 501 /error/50x.html
ErrorDocument 502 /error/50x.html ErrorDocument
503 /error/50x.html Mozilla/2" nokeepalive BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0 BrowserMatch "RealPlayer 4\.0" force-response-1.0 BrowserMatch "Java/1\.0" force-response-1.0 BrowserMatch "JDK/1\.0" force-response-1.0 BrowserMatch "Microsoft Data Access Internet Publishing Provider" redirect-care$ BrowserMatch "MS FrontPage" redirect-carefully BrowserMatch "^WebDrive"
BrowserMatch "^WebDAVFS/1.[0123]" redirect-carefully
BrowserMatch "^gnome-vfs/1.0" redirect-carefully
BrowserMatch "^XML Spy" redirect-carefully
BrowserMatch "^Dreamweaver-WebDAV-SCM1" redirect-carefully

Answer 1

This is a general error about connecting to mysql failed for one reason or another, the possible options are:
1 mysql is busy - hangs and does not respond
2 max_connections value is too high
3 mysql is not started or restarted after a crash/segfault
Recommendations:
1 during problems execute in the console mysqladmin pr (however, if mysql is really bad, it may also not work)
2 enable mysql logs and see what happens there during problemsv
3 configure mysql monitoring using zabbix/cacti/munin/whatever (you need graphs for the number of connections and what actually mysql is doing)